Monday, January 25, 2010

I needed to implement zero-copy for a block device driver. It turned out that a lot of IO in the driver was happening through buffers and earlier each IO involved page allocations and copying of data from page to buffer. This naturally ate up lot of CPU and needed improvements.

While implementing I did not find good example code in Linux kernel, due to which I ended up wasting some time in investigations. Some issues to consider:

1) Don't assume that all memory was kmalloc'ed. Check using is_vmalloc_addr() what type of memory it is.
2) On some architectures, even kmalloc allocations will cross page boundaries

Monday, January 18, 2010

I have been working on a Linux kernel replication product and have been wanting to profile the kernel module for evaluating performance. I used OProfile as the tool for extracting the profiling information.

1. Install kernel-debuginfo packages or compile a kernel since we need vmlinux

2. Since I was working with VMWare, I needed to load oprofile module and use timer interrupts
modprobe oprofile timer=1
This took a little bit of time to figure out. If this step is not done, then you would not see any logs even though you would not see any errors.

Saturday, January 16, 2010

There are tens of thousands of businesses making many millions a year in profits that still haven’t ever heard of twitter, blogs or facebook. Are they all wrong? Have they missed out or is the joke really on us? They do business through personal relationships, by delivering great customer service and it’s working for them. They’re more successful than most of those businesses who spend hours pontificating about how others lose out by missing social media and the latest wave. And yet they’re doing business. Great business. Not writing about it. Doing it.

I’m continually amazed by the number of people on Twitter and on blogs, and the growth of people (and brands) on facebook. But I’m also amazed by how so many of us are spending our time. The echo chamber we’re building is getting larger and louder.

More megaphones don’t equal a better dialogue. We’ve become slaves to our mobile devices and the glow of our screens. It used to be much more simple and, somewhere, simple turned into slow.

We walk the streets with our heads down staring into 3-inch screens while the world whisks by doing the same. And yet we’re convinced we are more connected to each other than ever before. Multi-tasking has become a badge of honor. I want to know why.

I don’t have all the answers to these questions but I find myself thinking about them more and more. In between tweets, blog posts and facebook updates.

I tend to agree with him, especially the first paragraph. Twitter, Facebook and rest of the social media are certainly redefining virtual relationships and helping to create personal relationships. So while social media is a very important medium to reach more people, we mustn't forget that reaching people is only half the job done.